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SUMMARY: Genes which are involved in anaerobic growth with nitrate or nitrite as terminal electron acceptor in Pseudomonas aeruginosa were mapped by interrupted mating and linkage analysis after conjugation. Times of entry were mostly consistent with the linkage frequencies. Late markers were not located precisely. A gene order was obtained for the genes involved in dissimilatory nitrate (nar) and nitrite reduction (nir) and anaerobical growth (ana) and for some already known auxotrophic genes. A mutant unable to grow aerobically (aer) was found. The aer mutation appeared to be an early marker. The cytochrome spectra of nir mutants and part of the cytochrome oxidase activities were abnormal in that haem d was absent. Most of the nar mutants were pleiotropic. Nar A mutants were affected in assimilatory and dissimilatory nitrate reductase, and nar B, nar D and nar E mutants lacked assimilatory and dissimilatory nitrate reductase and xanthine dehydrogenase. In nar D mutants high concentrations of molybdate restored xanthine dehydrogenase and assimilatory and dissimilatory nitrate reductase and, consequently, anaerobic growth. Just as in the aer mutants, which had a normal respiratory system, the denitrifying system and the cytochrome system in ana mutants were normal. It is therefore unlikely that ana and aer mutants synthesize defective energy generating systems.
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